Thiophene Separation with Silver-Doped Cu-BTC Metal-Organic Framework for Deep Desulfurization

Molecular simulations using grand-canonical ensemble Monte Carlo (GCMC) and first-principles calculations were performed to study the silver doped copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC) metal organic framework (MOF) for deep desulfurization. The density function theory (DFT) calculations were conducted to quantify the binding energies of silver dopant with Cu-BTC as well as adsorbates. The computed DFT potentials were taken to parametrize the classical host guest force fields for GCMC simulations with high accuracy. Adsorption isotherms of thiophene and toluene in isooctane solutions were experimentally measured using pure Cu-BTC samples for the validation of molecular modeling. The simulation results show that the doping of silver leads to significant increase of adsorption uptakes for all components (thiophene, toluene, and isooctane), agreeing with the results of calculated adsorption enthalpies in Ag-Cu-BTC. Simulation snapshots reveal that thiophene is preferentially accommodated in the small tetrahedral cage of Cu-BTC, before intruding into the large octahedral cages to suppress loadings of toluene and isooctane with the assistance of silver dopants. The resulting selectivity of thiophene to toluene in isooctane was as high as 4 in Ag-Cu-BTC. On the basis of the mechanistic understandings, screen criteria and fictionalization schemes of potential MOF materials are proposed for applications of adsorptive desulfurization.